<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>浮动布局</title>
</head>

<style>
  body {
    margin: 0;
  }
  .container {
    height: 100vh;
  }
  .aside {
    float: left;

    width: 200px;
    height: 100%;
    background-color: darkcyan;
  }
  .main {
    margin-left: 200px;

    height: 100%;
    background-color: darkgreen;
  }
</style>

<body>
  <div class="container">
    <div class="aside"></div>
    <div class="main"></div>
  </div>
</body>
</html>